Electroluminescent device with barrier layer structure, method for manufacturing the same, and electronic apparatus

ABSTRACT

The invention provides a low-profile electroluminescent (EL) device, a method for manufacturing the same, and a low-profile electronic apparatus. The EL device can include first electrodes, EL layers disposed on the first electrodes, a second electrode to cover the EL layers, and a barrier layer in contact with the second electrode. At least the surface of the second electrode facing the barrier layer can be composed of an inorganic oxide. At least the surface of the barrier layer facing the second electrode can be composed of an inorganic compound.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to an electroluminescent device, a methodfor manufacturing the same, and an electronic apparatus incorporatingthe same.

2. Description of Related Art

Since an electroluminescent (EL) component is vulnerable to moisture andoxygen, the component is sealed with a sealing substrate, which isformed by carving a glass substrate. Methods for carving the glasssubstrate include, for example, wet etching, sand blasting, and molding.However, each of these methods has advantages and disadvantages in termsof the processing time, the number of steps, and the cost. Furthermore,it is difficult to achieve a low-profile EL device sealing withsubstrate composed of a glass substrate.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a low-profile ELdevice, a method for manufacturing the same, and a low-profileelectronic apparatus.

An EL device according to the present invention can include a firstelectrode, EL layers disposed on the first electrode, a second electrodedisposed to cover the EL layers, and a barrier layer in direct contactwith the second electrode. At least the surface of the second electrodefacing the barrier layer is composed of an inorganic oxide, and at leastthe surface of the barrier layer facing the second electrode is composedof an inorganic compound.

According to the present invention, the surface having an inorganiccompound of the barrier layer directly can contact with the surfacehaving an inorganic oxide of the second electrode, thereby improving thegas barrier characteristics of the barrier layer. Furthermore, thebarrier layer is directly disposed on the second electrode, therebyachieving a low-profile EL device.

In the EL device, the second electrode may be composed of indium tinoxide or indium zinc oxide.

In the EL device, the second electrode may cover side faces and upperfaces of the EL layers.

In the EL device, the barrier layer may be composed of at least onesublayer composed of a silicon compound.

In the EL device, the barrier layer may include a sublayer in contactwith the second electrode, the sublayer being composed of silicon oxide.

In the EL device, the barrier layer may include a sublayer in contactwith the second electrode, the sublayer being composed of siliconnitride.

In the EL device, the barrier layer may include a sublayer in contactwith the second electrode, the sublayer being composed of siliconnitride oxide.

The EL device may further include an insulating layer disposed aroundthe second electrode, the insulating layer being composed of a siliconcompound. The barrier layer extends over the insulating layer.

The EL device may further include a protective layer for covering thebarrier layer.

The EL device may further include an adhesive layer disposed between thebarrier layer and the protective layer.

In the EL device, the adhesive layer may be composed of a materialsofter than that of the protective layer.

An electronic apparatus according to the present invention includes theabove EL device.

A method for manufacturing an EL device according to the presentinvention includes the steps of forming a second electrode to coverelectroluminescent layers disposed on a first electrode, the secondelectrode having a surface being composed of an inorganic oxide, andforming a barrier layer such that at least one portion of the barrierlayer comes into direct contact with the second electrode, the barrierlayer being composed of an inorganic compound.

According to the present invention, at least one portion of the barrierlayer, which is composed of an inorganic compound, can be formed suchthat the barrier layer directly contacts the surface composed of aninorganic oxide of the second electrode. Therefore, the gas barriercharacteristics of the barrier layer are improved. Since the barrierlayer is directly formed on the second electrode, a low-profile ELdevice can be achieved.

In the method for manufacturing an EL device, the second electrode maybe formed by vapor phase deposition.

In the method for manufacturing an EL device, the barrier layer may beformed by vapor phase deposition.

In the method for manufacturing an EL device, the second electrode maybe composed of indium tin oxide or indium zinc oxide.

In the method for manufacturing an EL device, the barrier layer may becomposed of a silicon compound.

In the method for manufacturing an EL device, the barrier layer may havea sublayer in contact with the second electrode, the sublayer beingcomposed of silicon oxide.

In the method for manufacturing an EL device, the barrier layer may havea sublayer in contact with the second electrode, the sublayer beingcomposed of silicon nitride.

In the method for manufacturing an EL device, the barrier layer may havea sublayer in contact with the second electrode, the sublayer beingcomposed of silicon nitride oxide.

In the method for manufacturing an EL device, the barrier layer mayextend over an insulating layer disposed around the second electrode,the insulating layer being composed of a silicon compound.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numerals reference like elements, and wherein:

FIG. 1 illustrates an EL device according to a first embodiment of thepresent invention;

FIG. 2 is a sectional view of the EL device according to the firstembodiment of the present invention;

FIG. 3 is a circuit diagram of the EL device according to the firstembodiment of the present invention;

FIG. 4 is a sectional view of an EL device according to a secondembodiment of the present invention;

FIG. 5 is a sectional view of an EL device according to a thirdembodiment of the present invention;

FIG. 6 illustrates an electronic apparatus according to an embodiment ofthe present invention; and

FIG. 7 illustrates an electronic apparatus according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The embodiments according to the present invention will now be describedwith reference to the drawings. FIG. 1 illustrates an electroluminescent(EL) device according to a first embodiment of the present invention. AnEL device 10 includes a substrate 12. The substrate 12 may be a glasssubstrate, a plastic substrate, or a silicon substrate. If the EL device10 is a top-emission-type device wherein light is emitted from theopposite side of the substrate 12, the substrate 12 does not requireoptical transparency. On the other hand, if the EL device 10 is abottom-emission-type device wherein light is emitted from above thesubstrate 12, the substrate 12 requires optical transparency.

The EL device 10 includes a pair of scanning drivers 14. The scanningdrivers 14 may be chips or thin film circuits (for example, circuitshaving TFTs) disposed on the substrate 12.

The EL device 10 can include a plurality of anode lines 16, 18, and 20.The anode lines 16, 18, and 20 are lines for applying an electriccurrent to EL layers 40 (see FIG. 2). The anode lines 16, 18, and 20have different widths. This structure is suited to apply differentamounts of current depending on the difference in luminous efficiencyfor the colors (R, G, B) of the EL layers 40. The EL device 10 includesa cathode line 22. The cathode line 22 is disposed outside of the anodelines 16, 18, and 20. The cathode line 22 is disposed in a U shape (or aC shape) so as to be away from the side for installing a wiring board.

FIG. 2 is a sectional view of the EL device according to the embodimentof the present invention. The EL device 10 can include a plurality offirst electrodes 30. Each of the first electrodes 30 is electricallyconnected to a corresponding one of the anode lines 16, 18, and 20. Ifthe substrate 12 is not composed of an electrical insulator, aninsulating layer 32 may be formed between the first electrodes 30 andthe substrate 12. If the substrate 12 is composed of silicon, theinsulating layer 32 may be composed of a silicon compound (for example,silicon oxide, silicon nitride, or silicon nitride oxide). Theinsulating layer 32 may be composed of plural layers. A part of theinsulating layer 32 may be disposed at the side faces of the firstelectrodes 30. The first electrodes 30 and the insulating layer 32 maybe flush.

The EL device 10 includes switching elements 34 for regulating thecurrent to the first electrodes 30. The switching elements 34 may becovered with the insulating layer 32.

The EL layers 40 are formed on each of the first electrodes 30. The ELlayers 40 include a luminescent layer 42. The luminescent layer 42 iscomposed of high molecular weight or low molecular weight organicmaterial. The luminescent layer 42 emits light by carrier injection. TheEL layers 40 may have a composition wherein the luminescent layer 42 issandwiched between a hole transport layer 44 and an electron transportlayer 46. A bank layer 48 is formed between the adjacent EL layers 40.The bank layer 48 is composed of an electrical insulator, which shieldsthe electrical connection between each of the adjacent EL layers 40. Thebank layer 48 may be composed of a silicon compound (for example,silicon oxide, silicon nitride, or silicon nitride oxide).

The EL device 10 can include a second electrode 50. The second electrode50 is formed to cover the EL layers 40 (for example, the side faces andthe upper faces of the EL layers 40). The second electrode 50 may coverall of the EL layers 40. The second electrode 50 may cover the banklayer 48. The second electrode 50 may be disposed to cover all of thefirst electrodes 30. The second electrode 50 may be transparent. Atleast one surface of the second electrode 50 (a surface facing a barrierlayer 52) is composed of inorganic oxide. The second electrode 50 may becomposed of indium tin oxide or indium zinc oxide. The second electrode50 is electrically connected to the cathode line 22. A part of theinsulating layer 32 may be disposed around the second electrode 50 (forexample, at the bottom of the second electrode 50).

The EL device 10 can include the barrier layer 52, which is composed ofat least one sublayer 53. The barrier layer 52 is transparent (forexample, the barrier layer 52 has an optical transmittance of at least80%). The barrier layer 52 is formed in contact with the secondelectrode 50. At least the surface of the barrier layer 52 facing thesecond electrode 50 is composed of an inorganic compound (for example, asilicon compound such as silicon oxide, silicon nitride, or siliconnitride oxide). The barrier layer 52 may include at least one sublayercomposed of a silicon compound. The barrier layer 52 may include asublayer composed of silicon oxide or silicon nitride, the sublayercontacting with the second electrode 50. The barrier layer 52 extendsover the insulating layer 32. The barrier layer 52 has a thicknessranging from 10 nm to 300 nm, for example about 100 nm.

According to the present embodiment, the surface having an inorganiccompound of the barrier layer 52 directly contacts with the surfacehaving an inorganic oxide of the second electrode 50, thereby improvingthe gas barrier characteristics of the barrier layer 52. Also, the gasbarrier characteristics are improved at the sublayer of the barrierlayer 52 composed of the silicon compound, which is disposed on theinsulating layer 32 (for example, the bottom part of the barrier layer52). Furthermore, the barrier layer 52 is directly formed on the secondelectrode 50, thereby achieving a low-profile EL device 10.

A protective layer 54 may be formed on the barrier layer 52. Theprotective layer 54 is transparent (for example, the protective layer 54has an optical transmittance of at least 80%). The protective layer 54has durability or an anti-reflecting function, and may have a gasbarrier ability. The protective layer 54 may be composed of, forexample, glass, a plastic film, a polymer layer including carbon atoms,diamond-like carbon, and a fluorocarbon polymer.

Referring to FIG. 1, a wiring board 60 is attached to the EL device 10,thereby composing an EL module. The wiring board 60 includes a substrate62. The substrate 62 may be a flexible substrate. Wiring patterns (notshown in the figure) are formed on the substrate 62. Anisotropicconductive materials (such as an anisotropic conducting film and ananisotropic conducting paste) may be used for electrically connectingthe EL device 10 and the wiring board 60.

An integrated circuit chip 64 is mounted on the wiring board 60. Asignal driver having a function for generating signals to the EL device10 may be formed in the integrated circuit chip 64. The integratedcircuit chip 64 may be electrically connected to the substrate 62 byflip-chip bonding or tape automated bonding (i.e., TAB).

The EL device according to the present embodiment can be composed asdescribed above, and the manufacturing method of the EL device will nowbe described. In the method for manufacturing the EL device, the secondelectrode 50 is formed to cover the EL layers 40 disposed on the firstelectrodes 30, the second electrode 50 having a surface composed of aninorganic oxide. Then the barrier layer 52 is formed such that at leastone portion of the barrier layer 52 directly contacts with the secondelectrode 50, the barrier layer 52 being composed of an inorganiccompound.

The second electrode 50 may be formed by vapor phase deposition (such assputtering and chemical vapor deposition (CVD)). The barrier layer 52may be formed by vapor phase deposition (such as sputtering and chemicalvapor deposition (CVD)). The vapor phase deposition may be performed ina reduced pressure atmosphere. Since other conditions are the same as inthe description of the above EL device, the conditions are notdescribed.

According to the present embodiment, at least one portion of the barrierlayer 52, which is composed of an inorganic compound, is formed suchthat the barrier layer 52 directly contacts the surface composed of aninorganic oxide of the second electrode 50. Therefore, the gas barriercharacteristics of the barrier layer 52 are improved. Since the barrierlayer 52 is directly formed on the second electrode 50, a low-profile ELdevice 10 can be achieved.

FIG. 3 illustrates a circuit of an EL module including an EL deviceaccording to the present embodiment. The EL device 10 includes aplurality of scanning lines 70, a plurality of signal lines 72 extendingin the direction perpendicular to the scanning lines 70, and a pluralityof power lines 74 extending in the direction parallel to the signallines 72. The scanning lines 70 are electrically connected to thescanning drivers 14 (for example, the scanning drivers 14 include shiftregisters and level shifters). Signal lines 72 are electricallyconnected to the signal driver 76 of the integrated circuit chip 64. Thepower lines 74 are electrically connected to the corresponding anodelines 16, 18, and 20. The EL layers 40, which form pixels, arecorrespondingly disposed at each intersection of the scanning lines 70and the signal lines 72.

The switching elements 34 are electrically connected to the scanninglines 70, corresponding to the pixels. If the switching elements 34 arecomposed of thin-film transistors (metal-oxide semiconductorfield-effect transistors (MOSFETs)), the scanning lines 70 areelectrically connected to gate electrodes of the transistors. Capacitors80 are electrically connected to the signal lines 72, corresponding tothe pixels. Specifically, the capacitors 80 are electrically connectedbetween the corresponding signal lines 72 and the power lines 74, andthe capacitors 80 hold electric charges corresponding to picture signalsfrom the signal lines 72. The switching elements 34 are electricallyconnected between the corresponding capacitors 80 and the signal lines72. The switching elements 34 are controlled by scanning signals fromthe scanning lines 70. The switching elements 34 control chargeaccumulation to the capacitors 80.

Driving elements 82 are regulated depending on the amount of electriccharges held in the capacitors 80, or whether or not electric chargesexist. If the driving elements 82 are composed of thin-film transistors(metal-oxide semiconductor field-effect transistors (MOSFETs)), gateelectrodes of the transistors are electrically connected to electrodesof the capacitors 80, the electrodes being disposed at the signal line72 side. The driving elements 82 are electrically connected between thecorresponding power lines 74 and the EL layers 40. Accordingly, thedriving elements 82 regulate the current supply from the power lines 74to the EL layers 40.

According to this composition, when the switching elements 34 are placedin the ON state by scanning signals from the signal lines 72, electriccharges are held at the capacitors 80 due to the difference in potentialbetween the signal lines 72 and the power lines 74. The control state ofthe driving elements 82 depends on the electric charges. Then currentflows from the power lines 74 to the first electrodes 30 throughchannels of the driving elements 82, and to the second electrode 50through the EL layers 40. The EL layers 40 emit light depending on theamount of current flowing therethrough.

FIG. 4 illustrates an EL device according to a second embodiment of thepresent invention. According to this embodiment, a second electrode 100includes an upper portion covering the upper part of the EL layers 40,side portions extending down from the upper portion, and flange portions102 extending from the side portions towards the outside. A barrierlayer 110 includes an upper barrier portion contacting the upper portionof the second electrode 100, side barrier portions contacting the sideportions of the second electrode 100, and flange barrier portions 112contacting the flange portions 102 of the second electrode 100.According to the present embodiment, the barrier layer 110 has flangebarrier portions 112, thereby sealing the area from the EL layers 40 toa position away from the EL layers 40. Therefore, the gas barriercharacteristics are further improved. Other compositions, manufacturingmethods, and operations and advantages correspond to the descriptionaccording to the first embodiment.

FIG. 5 illustrates an EL device according to a third embodiment of thepresent invention. According to the present embodiment, an adhesivelayer 120 is disposed on a barrier layer 52. Furthermore, a protectivelayer 122 is disposed on the adhesive layer 120. The protective layer122 corresponds to the protective layer 54 described in the firstembodiment. The adhesive layer 120 may be composed of, for example,polyurethane resin, acrylic resin, epoxy resin, and polyolefin. Theadhesive layer 120 is transparent. If the adhesive layer 120 is composedof a material softer than that of the protective layer 122 (for example,a material having a low glass transition point), the adhesive layer 120absorbs external impacts. Other compositions, manufacturing methods, andoperations and advantages correspond to the description according to thefirst embodiment.

As examples of electronic apparatuses having an EL device according tothe present invention, FIG. 6 illustrates a notebook personal computer1000, and FIG. 7 illustrates a cell phone 2000.

It should be understood that the present invention is not limited to theabove embodiments and various modifications are possible. For example,the present invention includes substantially the same compositions (forexample, compositions having the same functions, manufacturing methods,and results, or compositions having the same objects and results)described in the above embodiments. The present invention can includecompositions wherein non-essential parts of the composition described inthe above embodiments are substituted. The present invention includescompositions resulting in the same operations and the same advantages,or compositions achieving the same objects described in the aboveembodiments. Furthermore, the present invention includes compositionswherein conventional-art materials are added to the compositionsdescribed in the above embodiments.

Experiments have been performed to confirm the advantages of the presentinvention. A barrier layer composed of an inorganic compound, aninorganic oxide layer, a metal layer, and a resin layer were used in theexperiments.

The barrier layer was deposited by electron cyclotron resonance plasmasputtering. Si was used as a target material. The degree of vacuum was0.2 Pa, and Ar and O₂ were introduced. The layer had a thickness of 70nm.

The inorganic oxide layer was deposited by magnetron DC sputtering.InSnO was used as a target material. The degree of vacuum was 0.4 Pa,and Ar and O₂ were introduced. The layer had a thickness of 100 nm.

The metal layer was deposited by resistance heating evaporation. Highpurity Al was used as a material. The degree of vacuum was 1.0×10⁻⁵ Pa.The layer had a thickness of 100 nm.

The resin layer was composed of polyethylene terephthalate. The layerhad a thickness of 188 μm.

A water vapor permeability (g/m².24 hours: 60° C. 90% RH) was measuredaccording to JIS-Z0208 (Japanese Industrial Standards). The results wereas follows.

The water vapor permeability of a layered product including the resinlayer, the inorganic oxide layer, and the barrier layer was 0.04.Accordingly, the water vapor permeability of the barrier layer wascalculated to be 0.04.

The water vapor permeability of a layered product including the resinlayer and the barrier layer was 1.76. Accordingly, the water vaporpermeability of the barrier layer was calculated to be 2.18.

The water vapor permeability of a layered product including the resinlayer, the metal layer, and the barrier layer was 0.41. Accordingly, thewater vapor permeability of the barrier layer was calculated to be 0.81.The water vapor permeability of the resin layer was 9.19.

According to the above experimental results, when the barrier layercomposed of the inorganic compound was deposited on the inorganic oxidelayer, the lowest water vapor permeability (the highest gas barriercapacity) was achieved. This result validates the advantages of thepresent invention.

1. An electroluminescent device, comprising: first electrodes;electroluminescent layers disposed over the first electrodes; a secondelectrode disposed over the electroluminescent layers and having a firstsurface that includes an inorganic oxide; and a barrier layer having asecond surface that includes an inorganic compound, the second surfaceof the barrier layer being in direct contact with the first surface ofthe second electrode.
 2. The electroluminescent device according toclaim 1, the second electrode including indium tin oxide or indium zincoxide.
 3. The electroluminescent device according to claim 1, the secondelectrode covering side faces and upper faces of the electroluminescentlayers.
 4. The electroluminescent device according to claim 1, thebarrier layer including at least one sublayer composed of a siliconcompound.
 5. The electroluminescent device according to claim 4, thebarrier layer including a sublayer in contact with the second electrode,the sublayer being composed of silicon oxide.
 6. The electroluminescentdevice according to claim 4, the barrier layer including a sublayer incontact with the second electrode, the sublayer being composed ofsilicon nitride.
 7. The electroluminescent device according to claim 4,the barrier layer including a sublayer in contact with the secondelectrode, the sublayer being composed of silicon nitride oxide.
 8. Theelectroluminescent device according to claim 1, further comprising: aninsulating layer disposed around the second electrode, the insulatinglayer being composed of a silicon compound, the barrier layer extendingto the insulating layer.
 9. The electroluminescent device according toclaim 1, further comprising: a protective layer that covers the barrierlayer.
 10. The electroluminescent device according to claim 9, furthercomprising: an adhesive layer disposed between the barrier layer and theprotective layer.
 11. The electroluminescent device according to claim10, the adhesive layer including a material that is softer than that ofthe protective layer.
 12. An electronic apparatus comprising theelectroluminescent device according to claim
 1. 13. Anelectroluminescent device comprising: first electrodes;electroluminescent layers being disposed over the first electrodes; asecond electrode being disposed over the electroluminescent layers andincluding an inorganic oxide; and a barrier layer including an inorganiccompound, the inorganic oxide of the second electrode directlycontacting the inorganic compound of the barrier layer.
 14. Anelectroluminescent device comprising: first electrodes;electroluminescent layers disposed over the first electrodes; a secondelectrode being disposed over the electroluminescent layers andincluding an inorganic oxide; and a barrier layer being disposed on thesecond electrode and including silicon compound, the inorganic oxide ofthe second electrode directly contacting the silicon compound of thebarrier layer.
 15. An electroluminescent device comprising: anodes;electroluminescent layers disposed over the anodes; a cathode beingdisposed over the electroluminescent layers and including an inorganicconductive oxide; and a barrier layer including an inorganic compound,the inorganic conductive oxide of the cathode directly contacting theinorganic compound of the barrier layer.